Not long after ``Executioner,'' the first movie to be filmed in a real prison, and ``The Actresses,'' featuring a rare all-female cast, comes ``Harmony,'' about women living behind bars in tune to a different synchronization.

Kim Yun-jin returns to the local screen two years after starring in the hit thriller ``Seven Days.'' The ``Lost'' star has shed her serious image to wear an unfading smile and a blue jail uniform in the tearjerker family drama.

``It's a movie for which we had to reshoot scenes because we cried too much,'' the actress said Monday in Seoul following the film's press preview. Produced by ``Haeundae'' director Yun Je-kyoon and directed by newcomer Kang Dae-gyu, the movie is indeed designed to draw out tears ― and despite some oddly placed musical moments and mainstream superficiality, it works.

Kim stars as Jeong-hye, who, after killing her abusive husband, is sentenced to serve 10 years in Cheongju Women's Prison. She gives birth to a baby boy during the stint and tries to cherish every bit of the 18 months she has with Min-ho before giving him up for adoption, in accordance with the law.

One day she is impressed by a visiting choir and sets out to start one her own. The kindhearted prison chief promises Jeong-hye a special outing with Min-ho if she succeeds.

But contrary to the film's title, the protagonist is severely tone deaf and her pitchy lullabies induce tearful fits, rather than sleep, from Min-ho. Yet this happy-go-lucky story makes sure its protagonist never loses her smile, and she finds help in her prison mate Mun-ok, a former music professor on death row. Veteran actress Na Moon-hee gives weight and a compelling spin to the melodrama.

Also joining in the harmony are a comic duo of girlfriends, a night club singer and professional wrestler (played by musical actresses Jung Su-yeong and Park Jun-myeon, respectively) and a young soprano with a dark past (``Haeundae'' starlet Kang Ye-won, who actually majored in music in college).

Shooting the film in an actual prison ― though it was limited to mostly public areas such as the rooftop and courtyard ― proved to be a special experience for the cast.

Na said witnessing an elderly woman make haste to visit her child helped her interpret her character, who does not give up trying to reach out to her children, who had shunned their convict mother. Kim recalls a moment when an inmate started singing along with her from inside a cell when she was rehearing in the hall.

``Harmony'' rings with strong sorority spirit, featuring the women making the most of their cohabitation in a tiny space ― using empty toilet paper rolls as hair rollers and working with a piece of yarn to slice up a watermelon.

``I've never been offered the chance to play a character like Jeong-hye, who makes such a beautiful effort under desperate conditions. I accepted it without second thought,'' said Kim.

The movie casts the characters, who are sentenced for some serious offenses, under a sympathetic light ― as victims of rape, fraud or heartbreak.

``I found out through research that most women commit accidental crimes. I did not however attempt to tell a story on their behalf; rather I aimed to tell a story about family ties, how people try to connect with family even under tough conditions. It's a story about a different form of family,'' said the director.

The movie is not so much a ``Sound of Music''-type bonding story through music; indeed the inmates rediscover hope through singing, but climactic moments follow after Jeong-hye gives up Min-ho for adoption. The choir has matured into a reputable ensemble, and the members are granted the opportunity to give a special performance and a special session to reunite with family members.